By: Dr. Nigel Maxted
School of Biosciences
University of Birmingham
Birmingham B15 2TT, UK
E-mail: [email protected]
How to Identify Vigna Specimens (text is adapted from Maslin, 2001)
To start the key:
1. Go to the directory that contains the interactive key.
2. Double-click on the “A key to African Vigna” icon and the front page of the key will appear.
The four windows display four lists:ists:
· Characters Available lists the characters that you may use to describe your specimen to the key; when you first start the key this will show a list of 90 characters.
· Character States Chosen will list the characters and their states as you select them; when you first start the key this window will be empty.
· Taxa Remaining lists the names of the taxa that 'match' your description; when you first start the key this window shows a list of the entire 60 species that are included in African Vigna data set.
· Taxa Discarded will list all those taxa that do not 'match your description; when you first start the key this window will be empty.
To identify a specimen (i.e. name a Vigna specimen):
Your aim is to match your unidentified specimen against the species descriptions held in the data set. As your description becomes more and more complete the key will progressively narrow down the list in Taxa Remaining until, hopefully, only one taxon remains - you have identified (in other words, named) the taxon to which your specimen belongs.
Characters and states
To select a character that you have chosen to score click on the name of the character in the Characters Available window and it will open to display its states. A character is any attribute referring to form, structure or behaviour which the taxonomist separates from the whole organism for a particular purpose such as comparison or interpretation. These are distinguished from character states which are the actual representation of that character found in a particular specimen. Thus a character, for example, “Corolla colour”, has multiple character states, yellow, pink, white, blue, purple, etc. Within the context of the interactive key there are two basic sorts of characters, multistate and numeric:
To select states of a character:
Click on the character name, which will ‘open’ the character to show the states, then either double-click the text of the state (e.g. “Corolla colour” in the above example) or drag it with the mouse into the Character States Chosen window; one or more character-states can be chosen in this way. You will now notice that some taxa - those with character-states that do not match your answer - will be moved from Taxa Remaining into Taxa Discarded.
As you answer more and more questions the list in Taxa Remaining will get shorter and shorter until, perhaps, only one remains.
Click on the character name, which will ‘open’ the character to show the states, then double-click the hash (#) symbol to the right of the orange information button (or drag it into Character States Chosen) and a box will pop up into which you can type the measurement: you can enter either a single number or a numeric range (with the two numbers separated by a hyphen [-]). To view other syntax options click on the blue hyperlink at the bottom of the dialogue box.
Apart from plant height, which is measured in metres, all other numeric measurements for the African Vigna data set are recorded in millimetres (but you do not have to type 'mm' into the box when you record your measurements). It will increase the likelihood of retaining the correct answer in Taxa Remaining if you enter a range of values (e.g. 3—6).
Which characters should you use?
When you first start the key, all 90 characters will be listed in the Characters Available window. You can answer questions in any order you wish, so you should be able to make an identification of your specimen based on the characters that are available. Use of dichotomous keys often fails because of the need to assess character states for characters that it is not possible to score on your specimen, e.g. seed characters are difficult to score as they are seldom present with a specimen. However, you can also ask the key itself to help by suggesting what is the appropriate character to use next (see Best and Bingo below) or compare descriptive information of the remaining taxa to see if you can match your specimen that way (see Similarities and Differences below) or scroll through the illustrations or photographs of the taxa remaining and see if your specimen matches any of them (see Slide show below).
The key opens with the full set of 90 characters that are available, but it is also possible to select a particular subset of characters, for example, if you only have vegetative material you may wish to use the vegetative characters alone and this may be achieved by selecting the vegetative character set. To select a particular character set click on characters, then click sets and check the small box to the left of the set name; you can load two or more sets simultaneously by checking more than one box. Now click anywhere outside the sets window and the characters contained in the set(s) you have selected will appear in the Characters Available window. The following sets of characters are available:
· All - This set contains the entire 90 characters which are available for use. This is the default set and when starting a new identification it is generally good practice to load this set and run Best (see below).
· Fast Find – This character set comprises the 29 characters that are generally easy to score and which have strong discriminating power.
· Vegetative - 31 characters relating to the vegetative characteristics of the plant.
· Inflorescence - 8 characters relating to the inflorescences.
· Flower - 27 characters relating to flowers.
· Fruit / legume - 12 characters relating to the fruit.
· Seed - 11 characters specific to seeds (including the hilum and aril).
· Distribution – This character set is composed of one character with seven states for the seven sub-regions of Africa:
It is advisable not to use geographic characters too early in your identification because of the possibility that yours is a new record for that region (which means that the correct answer will be eliminated from Taxa Remaining).
If you have a potential choice over which character to score next and are unsure which to choose you can ask for assistance. You do this by invoking the Best or Bingo options. Click on the Best button located on the toolbar and all characters in Characters Available will be checked to find those that, on average, will give you the shortest list in Taxa Remaining if you choose one of their states. If you can, answer one of these next. When you use the Best option the programme will either sort the characters, placing those with the strongest discriminating power at the top of the list, or find (and highlight) the next best character to use; you can decide which of these options you require by clicking on Characters then Best Options located on the menu bar.
The Bingo command also helps you to choose which character is appropriate to use next. Click on the Bingo button located on the toolbar and a window will appear showing various characters and their states (these will vary depending upon what taxa are left in Taxa Remaining). If your specimens possess any of the character states which are displayed then you will be left with just a single taxon in Taxa Remaining if you double-click that state.
Using Similarities and Differences
Click on the Similarities and Differences button located on the toolbar and you will see a Similarities and Differences tab. Each tab is divided into two panels: the upper one listing the characters and the lower one showing the taxa listed in Taxa Remaining with their character-state scores. Click on a character in the upper panel and the lower panel will display the states scored for that character for each of the remaining taxa. You can then compare the features of your specimen with the character-states for each taxon. Further options available under Similarities and Differences can be accessed at any time via the Lucid Help menu.
Using Slide Show
When you have reduced the number of taxa in Taxa Remaining to a few you can scroll through illustrations of them to see if any match your specimen. To do this click on the Taxa button located on the menu bar, then click on Slide Show and then All Remaining Taxa. Drawings of the remaining taxa will then automatically scroll on-screen (with a 4-second delay between images). You can control the slide show with the buttons located at the upper right-hand corner of the screen.
Starting a new identification
If you wish to restart the key after having identification a specimen then click the Restart button on the menu bar and this will clear both the Character States Chosen and Taxa Discarded windows. When you click this button a small window will appear, and by opening the drop-down list you will see that there are three options available concerning character sets for your new identification session: select one of these options then click on Restart. The characters that then appear in Characters Available will depend upon your selection.
Lucid is an easy to use knowledge management tool that can be used in the production of interactive identification systems. Lucid was developed by the Centre for Biological Information Technology (CBIT) at the University of Queensland. The Lucid system consists of a number of inter-related products that assist with the creation and use of keys (in any language) for any group of organisms. The software has standard system requirements and is available to either download or purchase. You can learn more about Lucid and the software available from the Lucid website: http://www.lucidcentral.org/.
Maslin, B.R. (Coordinator), 2001. Wattle: Accaias of Australia. ABRS and CALM, Canberra.